This invention relates generally to tacky polymeric microspheres, and has particular reference to inherently tacky, elastomeric, solvent-dispersible, solvent-insoluble, polymeric microspheres and a process for preparing same using a cationic emulsifier.
In U.S. Pat. No. 4,166,152, granted Aug. 28, 1979 to W. A. Baker et al., there is a disclosure of inherently tacky acrylate homopolymer microspheres prepared by aqueous suspension polymerization techniques utilizing a suspension stabilizer and an anionic emulsifier. The microspheres prepared by this method had an average particle size of 10-60 microns. The anionic emulsifiers retard particle coalescense by surrounding the particle with a negatively charged double layer which provides repulsion of the individual particles.
The inherently tacky, negatively charged microspheres disclosed by Baker have desirable properties in many applications where a low tack, reusable adhesive surface is desirable. All of these applications require that the microspheres be attached to sheet material as is disclosed for copolymer microspheres in U.S. Pat. No. 3,857,731, granted Dec. 31, 1974 to R. F. Merrill, Jr. et al. The Merrill et al patent suggests that copolymer microspheres, which also were prepared with an anionic emulsifier, can be anchored to the sheet material using a film-forming binder in which the copolymer microspheres are embedded. For some applications, it is desirable to have microspheres that are cationically (positively) charged to facilitate attachment to the sheet material. For example, paper has a slight anionical charge which should bond strongly to cationically charge microspheres. Comparisons of anionic and cationic surfactant microspheres coated on paper from a hexane solution demonstare that the cationic microspheres are tightly bonded to paper and do not have the transferance problems frequently noted with the anionic microspheres.
Other pertinent prior patents of which the applicant is aware are U.S. Pat. Nos. 3,513,120; 3,691,140; 3,857,731; 4,049,483 and 4,049,604.